This invention relates to an optical sensor array and, more particularly, to an optical sensor array for detecting current positions of plural moving objects such as, for example, keys and hammers incorporated in a keyboard musical instrument and a keyboard musical instrument using the same.
Several sorts of composite keyboard musical instruments are sold in the market. A composite keyboard musical instrument is a compromise between an acoustic keyboard musical instrument, i.e., a piano and an electronic keyboard. A player can selectively play a tune through acoustic sound and electronic sound. This sort of composite keyboard musical instrument has been known as xe2x80x9csilent pianoxe2x80x9d. When a pianist instructs the silent piano to enter the acoustic sound mode, a hammer stopper is moved out of the trajectories of hammers so as to permit the hammers selectively to strike the strings for generating the piano tones. On the other hand, if the pianist wishes to practice the fingering on the keyboard, he or she changes the silent piano to the silent mode. Then, the hammer stopper is moved into the trajectories of the hammers. While the pianist is fingering a tune on the keyboard, the action mechanism selectively drives the hammers for rotation. Although the hammers escape from the action mechanism, they rebound on the hammer stopper before striking the strings. No string vibrates. Thus, the pianist can practice the fingering without disturbance to his or her neighbors.
The silent piano is equipped with an electronic sound generating system. The electronic sound generating system comprises an array of key sensors, an array of hammer sensors, a data processing unit and a headphone. The array of key sensors is provided under the array of black and white keys, and supplies key position signals representative of the current key positions of the associated black and white keys to the data processing unit. On the other hand, the array of hammer sensors is provided in the vicinity of the array of the hammers, and supplies hammer position signals representative of the current hammer positions of the associated hammers to the data processing unit. The data processing unit periodically fetches the key position signals and hammer position signals from the signal ports assigned thereto, and accumulates pieces of data information representative of the variation of key/hammer position of each key/hammer in the data storage. The data processing unit periodically checks the data storage to see whether or not the pianist depresses any one of the black/white keys for generating a tone. If the data processing unit finds the pianist to depress a black/white key, the data processing unit determines the key velocity and timing at which the piano to is to be generated. The data processing unit produces music data codes representative of the tone to be produced, and converts the music data codes to an audio signal. The audio signal is supplied to the headphone, and the pianist hears the electronically produced tone through the headphone. Thus, the key/hammer sensors are indispensable component parts of the silent piano.
FIG. 1 shows a prior art optical sensor array 100. The prior art optical sensor array serves as the key sensors, and is provided under the array of black/white keys. Reference numeral 101 designates shutter plates. The shutter plates are attached to the black/white keys, respectively, and downwardly project from the lower surfaces of the associated black/white keys.
The prior art optical sensor array 100 largely comprises a supporting plate 103, plural sensor heads 104 and pairs of optical fibers 105/111. Slits 102 are formed in the supporting plate 103 at intervals, and the shutter plates 101 are aligned with the slits 102, respectively. The slits 102 are wider than the shutter plates 101, and permit the shutter plates 101 to be moved deeply into the space under the supporting plate 103.
The plural sensor heads 104 are attached to the supporting plate 103 at intervals, and are located on both sides of the slits 102. Thus, the sensor heads 104 are arranged such that the shutter plates 101 project into and are retracted from the gaps between the sensor heads 104.
The sensor heads 104 are formed of transparent acrylic resin, and have a configuration like a combination of large and small rectangular parallelepiped blocks. The small rectangular parallelepiped block projects from an end surface of the large rectangular parallelepiped block, and shoulders take place on both sides of the small rectangular parallelepiped block. A light outlet port 108 is provided on one of the shoulders, and a light inlet port 112 is provided on the other shoulder. The light outlet port 108 and light inlet port 112 of each sensor head 104 are aligned with the light inlet port 112 of one of the adjacent sensor heads 104 and the light outlet port 108 of the other adjacent sensor head 104. Thus, the light outlet ports 108 and the light inlet ports 112 are provided on optical paths.
A prism 106 and a collimator lens 107 as a whole constitute the light outlet port 108, and a condenser lens 109 and a prism 110 form in combination the light inlet port 112. Two holes are formed in the large rectangular parallelepiped block, and are open to the shoulders and the other end surface. The optical fiber 105 is inserted into one of the holes, and reaches the prism 106. The other optical fiber 111 is also inserted into the other hole, and reaches the prism 110.
Though not shown in FIG. 1, a light emitting device (not shown) is connected to the other end of the optical fiber 105, and a light detecting device is connected to the other end of the optical fiber 111. When the light emitting device is energized, light is radiated from the light emitting device into the optical fiber 105, and optical fiber 105 propagates the light to the prism 106. The light is reflected on the oblique surface of the prism 106, and is formed into a parallel ray through the collimator lens 107. The parallel ray proceeds toward the light inlet port 112 of the adjacent sensor head 104, and is incident into the light inlet port 112 of the adjacent sensor head 104.
The incident light is reflected on the oblique surface of the prism 110, and is fallen into the optical fiber 111. The optical fiber 111 propagates the light to the light detecting device, and the light detecting device converts the light to photo current.
A pianist is assumed to depress a black/white key. The black/white key is sunk, and, accordingly, the shutter plate 101 is moved downwardly. The shutter plate 101 reaches the optical path, and gradually interrupts the parallel ray. Accordingly, the amount of incident light is reduced, and the light detecting device reduces the photo-current. Thus, the current key position is converted to the amount of photo-current.
FIG. 2 shows another prior art optical sensor array. The prior art optical sensor array comprises the supporting plate 103, sensor heads 121/122 and optical fibers 105/111. The sensor heads 121/122 are alternated with the slits 102, and each sensor head 121/122 is associated with only one optical fiber 105/111.
The sensor head 121/122 comprises a body 121a and a pair of lenses 107/109. The body 121a has side surfaces parallel to each other, and the lenses 107/109 are attached to the side surfaces. A notch forms a pair of oblique surfaces 120 in the body 121a, and the optical fiber 105/111 is retained by the body 121a in such a manner that light is radiated to and received from the pair of oblique surfaces 120.
The optical fibers 105/111 are connected to a combined optical device, i.e., the combination of light-emitting and light-detecting elements. The combined optical device sequentially supplies light to the sensor heads 121. This means that the combined optical device supplies the light to the sensor head 121 on the right side of the sensor head 122 in a time slot and to another sensor head 121 on the left side of the sensor head 122 in another time slot. Although the sensor head 122 receives the light from both sensor heads 121, the timing is different between the sensor 121 head on the right side and the sensor head 121 on the left side so that the data processing unit can determine which the light source is.
Assuming now that the combined optical device supplies the light to the sensor head 121 on the right side of the sensor head 122, the light is radiated from the optical fiber 105 toward the oblique surfaces 120, and is reflected toward both side surfaces where the lenses 107 are attached. Thus, the light beam is split into two light beams, and is radiated through the lenses 107 toward the adjacent sensor heads. One of the split light beams is incident on the lens 109, and the incident light is reflected toward the optical fiber 111. The optical fiber 111 propagates the light to the combined optical device, and the light is converted to photo-current. The photo-current is converted to a key position signal, which is supplied to the data processing unit.
When the combined optical device supplies the light to the sensor head 121 on the left side, the light is incident on the sensor head 122. The right is reflected on the oblique surfaces 120, and the reflected light is incident on the optical fiber 111. The optical fiber 111 propagates the light to the combined optical device, and the combined optical device converts the light to photo-current. The photo-current is also converted to the key position signal, which is supplied to the data processing unit. The data processing unit discriminates the key position signal on the basis of the timing and the combination of the sensor heads 121/122.
The prior art optical sensor arrays are so compact that the manufacturer can install it in a narrow space inside the composite keyboard musical instrument.
In the above-described prior art optical sensor arrays, the sensor heads 104 and 121/122 are arranged on the rear surfaces of the supporting plates 103. The light outlet ports 108/107 are to be exactly aligned with the light inlet ports 112/109 of the adjacent sensor heads 104/122. For this reason, the assembling workers are expected to pay close attention to the assemblage.
The sensor heads 104 and 121/122 are fixed to the rear surfaces of the supporting plates 103 by means of adhesive compound. However, the adhesive compound requires a time for solidification. In order to keep the relative position between the sensor heads 104 and 121/122 and the supporting plates 103, the supporting plates are formed with holes, and projections are formed in the lower surfaces of the sensor heads 104 and 121/122. The holes and projections serve as a positioner, and the manufacturer gives a tight tolerance to the positioner. When an assembling worker locates the sensor head 104 or 121/122 at a target position on the lower surface of the supporting plate 103, he or she brings the sensor head 104 or 121/122 over the hole, and strongly presses it against the supporting plate 103. Then, the projection is forced into the hole. The assembling worker injects the sensor head 104 and 121/122 with adhesive compound. After a short time, the adhesive compound is solidified, and the sensor head 104 or 121/122 is fixed to the supporting plate 103.
The first problem inherent in the prior art optical sensor arrays is that the sensor heads 104 and 121/122 are liable to be broken in the assembling work. The sensor heads 104/121/122 measure 5-10 millimeters by 5-10 millimeters, and large force is required for inserting the projection into the hole due to the tight tolerance. The sensor heads 104/121/122 are not so strong that the small sensor heads 104/121/122 can not withstand the large force.
The second problem is low productivity. The sensor heads 104/121/122 are finally fixed to the supporting plates 103 by means of the adhesive compound, and the adhesive compound requires a time for solidification. This means that the assembling worker has to stand idle until the solidification of the adhesive compound. Even though the assembling worker starts the assembling work on another one before the solidification of the adhesive compound on the previous one, the assembling worker at the next stage still waits for the solidification of the adhesive compound on the previous one. Thus, the assembling workers consume a large amount of time and labor, and the manufacturer suffers from the low productivity.
The third problem inherent in the prior art optical sensor arrays is poor repairability. When an assembling worker fixes the sensor heads 104/121/122 to the supporting plate 103, the lenses 107/109 are liable to contaminated with the adhesive compound. Even if the assembling worker is notified immediately after injecting the adhesive compound, the assembling worker feels the separation of the contaminated sensor head 104/121/122 from the supporting plate 103 hard, because the projection is tightly received in the hole. If the assembling worker is notified after the solidification of the adhesive compound, it is impossible to separate the sensor head 104/121/122 from the supporting plate 103.
Thus, the prior art optical sensor arrays are breakable and poor in productivity and repairability. Nevertheless, the optical sensor arrays are indispensable for the composite keyboard musical instruments. This means that the prior art composite keyboard musical instruments are expensive. Thus, the prior art composite keyboard musical instrument has a problem in the production cost.
It is therefore an important object of the present invention to provide an optical sensor array, which is unbreakable, high in productivity and repairability.
It is also an important object of the present invention to provide a keyboard musical instrument, the production cost of which is improved by using the optical sensor array.
To accomplish the object, the present invention proposes to connect sensor heads to and located them at target positions on retaining portions through sliding motion of the sensor heads on the retaining portions.
In accordance with one aspect of the present inventor, there is provided an optical sensor array for converting current positions of moving objects to signals comprising a supporting plate having plural retaining portions at intervals, plural sensor heads respectively assigned to the plural retaining portions and establishing optical paths for light beams across the intervals, a combined optical device optically connected to the plural sensor heads and selectively supplying light to and receiving the light from the plural sensor heads through the optical paths, plural light modifiers connected to the moving objects and moved in the optical paths for modifying the light beams depending upon the current positions of the associated moving objects, and plural locating connectors formed partially in the plural sensor heads and partially in the plural retaining portions and connecting the plural sensor heads to target positions on the retaining portions through sliding motion of the sensor heads on the associated retaining portions.
In accordance with another aspect of the present invention, there is provided a keyboard musical instrument for generating audible tones from an electric signal comprising plural tone specifying mechanisms selectively actuated by a player for specifying tones to be generated, a tone generating unit generating the tones specified by the player through the plural tone specifying mechanisms, and an optical sensor array monitoring the plural tone specifying mechanisms so as to determine the tone specifying mechanisms actuated by the player and including a supporting plate having plural retaining portions at intervals, plural sensor heads respectively assigned to the plural retaining portions and establishing optical paths for light beams across the intervals, a combined optical device optically connected to the plural sensor heads and selectively to supplying light to and receiving the light from the plural sensor heads through the optical paths, plural light modifiers connected to the plural tone specifying mechanisms and moved in the optical paths for modifying the light beams depending upon the current positions of the associated tone specifying mechanisms and plural locating connectors formed partially in the plural sensor heads and partially in the plural retaining portions and connecting the plural sensor heads to target positions on the retaining portions through sliding motion of the sensor heads on the associated retaining portions.